1. Field of the Invention
The present invention generally relates to a brushless motor preferably used in a motor-driven power steering apparatus or the like.
2. Background Art
A brushless motor for a motor-driven power steering apparatus has a rotor having a permanent magnet and a stator provided with a plurality of coils. The rotor is rotated by switching a current application to the coil. The brushless motor is applied to a motor portion of the motor-driven power steering apparatus of a vehicle. For example, in a rack type motor-driven power steering apparatus, a coaxial type brushless motor is used, a rack shaft is inserted into a rotating shaft of the rotor, and the stator is formed in a housing side fixed to a vehicle body side. Further, in the brushless motor, in order to determine a timing for switching the current application to the coil, a resolver is provided as a position detecting sensor detecting a rotational position of the rotor with respect to the stator.
In the conventional motor-driven power steering apparatus, the resolver has a resolver stator attached to a side of the housing portion, and a resolver rotor attached to a side of the rotor. One such apparatus is described in Japanese Patent Application Laid-Open No. 2007-1364. In an assembling step for this motor-driven power steering apparatus, a positioning (a phase alignment and a spark advance regulation) is executed in a relative rotating direction of the resolver stator and the resolver rotor, by relatively rotating the housing portion with respect to the motor portion, in a state in which the motor portion and the housing portion are temporarily fixed so as to be relatively rotatable. This makes it possible to correct a phase shift (a shift of an attaching position in a relative rotating direction) generated at a time of assembling the resolver stator and the resolver rotor.
In the brushless motor described in the patent document 1, due to an increase of an assembling step and a man hour for executing the phase alignment of the resolver stator and the resolver rotor, and a necessity of making assembling holes of the motor portion and the housing portion long in correspondence to the phase alignment thereof, it is necessary to fix after the phase alignment, and a deterioration on a layout is caused, thereby increasing a cost.